1. Technical Field
The present invention relates to a display device for a vehicle including a self-luminous indicator with a display screen and a display control unit that displays the image information, which has a first display portion for fixedly displaying a given display pattern and a second display portion that is formed in a different region from the first display portion and has a lower brightness than the first display portion, on the display screen of the self-luminous indicator.
In addition, the present invention relates to a display device for a vehicle which displays a display pattern on a self-luminous indicator with a gradation defined by the image information.
2. Background Art
Generally, a display device for a vehicle provided in the vehicle interior of the vehicle is disposed in an instrument panel ahead of the driver's seat so that the driver sitting in the driver's seat can view the display of each instrumental device with a steering wheel interposed therebetween. The display device for a vehicle is configured to have a plurality of display areas showing the traveling speed of a vehicle, the number of revolutions per unit time of an engine, the remaining quantity of fuel in a fuel tank, the temperature of coolant for an engine, and the like. These display areas are efficiently arrayed in the same casing so that the driver can understand a vehicle state at a glance.
The display device for a vehicle may include a self-luminous indicator, such as an organic EL (Electro Luminescence) device, an inorganic EL device, a vacuum fluorescent display (VFD), and a field emission display (FED), so that display patterns, such as a speedometer and a tachometer, are displayed by the self-luminous indicator. Moreover, regarding such a self-luminous indicator, as disclosed in JP-A-2003-228329, it is known that the emission characteristic of a light emitting device deteriorates with an emission time and the brightness obtained by the same input current is decreased accordingly. Therefore, when the emission brightness of a specific pixel is high, for example, when an icon is always displayed at the fixed position of a screen, it is known that a problem of “burn-in” occurs that the emission characteristic of the pixel noticeably deteriorates compared with other pixels.
A matrix driving type display disclosed in JP-A-2003-228329 is based on a technical background in which the input data to each pixel is integrated for every pixel at fixed periods in a state where a display panel is being driven, the correction data for equalizing the integrated values for all pixels is created in the subsequent unused state, and each pixel is made to emit light on the basis of the correction data.
In the display disclosed in JP-A-2003-228329, however, it is necessary to monitor each pixel on the basis of the input data. In this case, since a circuit, which monitors an input signal to a light emitting device and stores the cumulative amount, and the like are required, hardware measures are necessary. For this reason, since a correction method, a circuit configuration, and the like should be also changed if a light emitting device used is changed, it is not suitable for general purpose.
Moreover, when adjusting the brightness of an image by software, there has been a problem that the data volume increases because a plurality of images for adjustment are used. When adjusting one image by software, there has been a problem that smooth drawing becomes difficult since the adjustment processing takes time or a problem that an expensive graphics controller needs to be used, for example. Therefore, taking mounting it in a vehicle into consideration, it has been difficult to realize it in terms of the costs and the like.
Particularly when the image information for fixed display has a plurality of kinds of display colors (gradations), it is necessary to monitor each item of the input data. As a result, there has been a problem that a correction method or the hardware configuration becomes complicated.
Moreover, when a display device for a vehicle is mounted in a vehicle, a warranty of ten years (3500 hours) is demanded. However, if an indicator is displayed with high brightness, there has been a problem that it is difficult to keep the brightness of the indicator constant during the warranty period and the display screen becomes dark as years go by. For this reason, when deterioration of the brightness of an indicator is noticeable, the indicator or the display device for a vehicle itself has to be exchanged.